Demand continues to increase for devices capable of obtaining a representative sample of water at a target depth, and for determining a water-sampling depth through a thorough analysis in a vertical groundwater flow pattern in a borehole when analyzing the quality of the groundwater.
Water samplers conventionally used include suction lift pumps, down-well centrifugal pumps, multi-level down-well sampling systems and passive diffusional samplers. Samplers using a pump may disturb the vertical flow of groundwater, thereby negatively impacting the accuracy of the samplers. In the case of passive diffusional samplers, an advantage exists in that groundwater flow disturbance does not occur. However, a shortcoming of passive diffusional samplers is that a week is required to sample groundwater. In the case of grab sampling devices (the most conventional type of which is a bailer), the possibility of flow disturbance is low by instantaneous groundwater sampling in a borehole, although there is a shortcoming that the depth of sampling cannot be specified.